Algae-based microbots deliver antibiotics to lungs

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Researchers from the University of California, San Diego have developed a microrobot system to treat bacterial pneumonia. The microrobots are made up of living algae cells that can swim very efficiently in biological fluids, allowing them to navigate the lungs and deliver drugs to hard-to-reach areas. Algae cells are studded with antibiotic-laden polymer spheres that are coated with neutrophil cell membranes, which help them neutralize inflammatory molecules released by bacteria in the lungs, providing a localized anti-inflammatory effect. In tests on mice with bacterial pneumonia, the microbots helped clear the infection. All treated mice survived for at least 30 days, while untreated mice died within three days.

Bacterial pneumonia can have disastrous consequences for patients, especially since it can often develop when a person is mechanically ventilated and already in serious condition. It can also be difficult to treat. Simply delivering large doses of antibiotics into the bloodstream may not work as well because very little of the dose ends up where it is needed in the lungs.

There is a need for more targeted and effective therapies. This prompted these UCSD researchers to create a localized therapy that can actively swim through the lungs and deliver drugs exactly where they’re needed. “Our goal is to deliver targeted drugs to more difficult parts of the body, such as the lungs,” said Liangfang Zhang, one of the creators of the new microrobots. “And we want to do it in a safe, easy, biocompatible and sustainable way. This is what we have demonstrated in this work.

Colored SEM image of a pneumonia-fighting microrobot consisting of an algae cell (green) coated with biodegradable polymer nanoparticles (brown). The nanoparticles contain antibiotics and are coated with neutrophil cell membranes. Image credit: Credit: Wang lab/UC San Diego, Fangyu Zhang and Zhengxing Li

The researchers chose algae as the delivery vector for antibiotics. Algal cells are very adept at swimming in biological fluids, such as the thick mucus that is usually present in the lungs of someone with pneumonia. They attached polymer spheres loaded with antibiotics to the outside of the algae cells and also coated the spheres with neutrophil membranes for additional anti-inflammatory action.

They tested the microrobots in mice with pneumonia caused by Pseudomonas aeruginosa. This type of pneumonia tends to occur in patients who have undergone mechanical ventilation and can be life threatening. The team introduced the microrobots into the lungs using a tube inserted into the trachea. In treated mice, the infection cleared after a week and all survived, while untreated mice died in as little as three days. The approach was also more effective than IV antibiotics, requiring a fraction of the dose to effectively treat the infection.

“With an IV injection, sometimes only a very small fraction of antibiotics enters the lungs. This is why many current antibiotic treatments for pneumonia do not work as well as needed, leading to very high death rates in the sickest patients,” said Victor Nizet, another researcher involved in the study. “Based on these mouse data, we see that microrobots could potentially improve the penetration of antibiotics to kill bacterial pathogens and save the lives of more patients.”

Study in Natural materials: Nanoparticle-modified microrobots for in vivo antibiotic delivery to treat acute bacterial pneumonia

Going through: UCSD

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